1. Field of the Invention
This invention relates to a method for chamfering a notch of a semiconductor wafer while keeping the wafer in implane self rotation and an apparatus for executing the method.
2. Description of the Prior Art
On account of effective application of photolithography, it has been customary for wafers such as semiconductor wafers to have an orientation flat (hereinafter referred to as "OF") formed thereon by grinding off to leave a short linear cut in part of the periphery of a wafer thereby facilitating correct positioning of the wafer on an exposure device.
The formation of the OF, however, inevitably results in removal of a large portion of the wafer. Particularly in the production of wafers of a large diameter, the cumulative amount of portions wasted by this removal is so large as to impair the yield of products conspicuously. The fact that this impaired yield prevents expensive semiconductor wafers from being efficiently utilized has posed a problem.
In the circumstances, the practice of imparting a notch substantially in the shape of the letter V or substantially in the shape of an arc to the periphery of a given wafer has come to prevail for the purpose of efficiently utilizing produced wafers. Particularly the V-shaped notches have been finding extensive utility by reason of their outstanding accuracy of positioning.
Since the wafers are destined to be conveyed a number of times on production lines as in the process for manufacture of devices, their peripheries are possibly subject to chippings on colliding with parts of equipment used in the manufacturing process and the produced semiconductor consequently suffer from degradation of characteristic properties. It has been customary, therefore, for the wafers to have their whole peripheral parts chamfered.
The wafers furnished with a notch as described above, however, have found no adaptability for any work of conventional chamfering technique because the notch is small in size as compared with the peripheral length of a wafer. As the semiconductor IC's have gained in number of components per chip, however, they come to entail the drawback that the notches of their wafers cause chippings when the wafers are positioned in the process of device production by aligning the notch to a pin of rigid material. Since sharp edges of the wafers are not easily removed by machining, the removal to be made at all adds conspicuously to occurrence of dust and the effort to preclude infliction of chippings fails. This fact has posed a problem too serious to be ignored.
This invention, initiated in the light of this problem, has for an object thereof the provision of a method for chamfering a notch of a wafer, which method is capable of easily and accurately chamfering a sharp edge such as of the notch and enabling the work of chamfering the notch to be carried out in high efficiency and an apparatus for executing the method.